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Tornadoes Tornadoes can occur anywhere, including the Northwest. They may not pose as large a risk as an earthquake, but small tornadoes can develop in severe thunderstorms or along convergence zones. Major Incidents
Issues to Note The Fujita or F-Scale ranks tornadoes from F0 (moderate damage to signs and small buildings) to F5 (incredible damage that disintegrates even strong frame houses). Tornado wind speeds range from 40-72 mph in an F0 to 73-112 mph in an F1, on up to 261-318mph in an F5 storm. Most tornadoes worldwide, and virtually all in the Northwest, are in F0 and F1 range although the table above is proof more powerful tornadoes occur in our region. Tornadoes are rare events, but the National Weather Service believes they have been under-reported in the Northwest because many people assume they cannot occur here. As King County develops and more eyes watch the sky, more reports have been made. As for vulnerability, on the positive side, Seattle doesn't have many buildings vulnerable to damage and on the negative side, it doesn't have an audible warning system except along the waterfront. Nationally, weak tornadoes only account for 4% of all fatalities. The probability of a deadly tornado in Seattle is extremely weak. On the Web The Tornado Project Online. A great database of all known tornadoes. Searchable by location. |
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